In recent years, awareness of conservation of global environment has been increasing more and more, and an attention has been paid to a fuel cell system including a fuel cell stack which is capable of supplying high-efficient energy (at least one of electric power and heat) as a product which contributes to the conservation of global environment. Such a fuel cell system includes a fuel processor to generate a fuel gas containing hydrogen.
The fuel processor is supplied with a raw material gas (e.g., natural gas, propane gas, etc.) and water and generates the fuel gas containing hydrogen through a reforming reaction between the raw material gas and water in a reforming catalyst stored in the fuel processor. The generated fuel gas is supplied to an anode of the fuel cell stack. An oxidizing gas (e.g., air or oxygen supplied from an oxygen tank) containing oxygen is supplied to a cathode of the fuel cell. The fuel cell stack carries out power generation by reacting hydrogen and oxygen electrochemically, thereby generating electric power and heat.
The water used in the reforming reaction in the fuel processor is stored in a water tank. The water is supplied from the water tank to the fuel processor. Before the fuel cell system carries out power generation for the first time after it is installed, tap water (city water) is supplied from outside to the water tank.
There has been proposed a fuel cell system having a water-filling mode (corresponding to “water-filling step” of the subject application) in which a water storage unit (corresponding to “first water tank” of the subject application) including a cooling water storage unit for storing cooling water for the fuel cell system is filled automatically with water from outside (see e.g., Patent Literature 1). In the fuel cell system disclosed in Patent Literature 1, a method is employed in which, when the fuel cell system is installed, the water filling mode is executed before carrying out a power generation operation, and the fuel cell system is started-up and starts power generation after filling of the water in the water storage unit and its pipes is completed.